[3] The distinctive feature of the skyscrapers, both inaugurated in 2014, is the presence of over ninety plant species, including tall shrubs and trees, distributed on the facades.

It is an ambitious project of metropolitan reforestation that aims to increase the biodiversity of plant and animal species in the Lombard capital through vertical greening, reducing urban sprawl and contributing to the mitigation of the microclimate.

This led to the replication of this experiment in the municipality of Shijiazhuang in the Hebei province of China, where a green and sustainable city was built in harmony with the environment.

Among the most vibrant sources of inspiration are the Casa nel Bosco (House in the Woods) by Cini Boeri, Stefano's mother, which was built in a birch forest and designed in a zigzag pattern to avoid the felling of trees.

[31] Among the precursors to the Bosco Verticale are also the utopian residences of Friedensreich Hundertwasser, with facades completely covered by the foliage of "tenant trees" (as the architect himself stated),[32] and the rooftop gardens of Emilio Ambasz, who operated according to an approach of "green on gray.

The numerous plant species distributed along the facades constitute a true ecosystem capable of attracting birds and insects (1,600 were counted in 2014),[40] "becoming an urban sensor for the spontaneous vegetal and animal recolonization of the city.

"[41]The Bosco Verticale [...] contributes [...] to the production of oxygen, the absorption of fine particles from traffic pollution, and the reduction of temperature fluctuations between the interior and the exterior.Another characteristic of the Vertical Forest is the ever-changing colors of the trees that cover its surfaces.

The plants have been strategically placed based on various formal and aesthetic criteria, including their ornamental qualities, flowering seasons, potential allergenicity, canopy and trunk development, and ease of maintenance.

The spectacle and visual experience will be different in each season.The following table presents the colors assumed by some of the plant species during the four seasons:[46] [47] Quercus ilex Quercus pubescens Koelreuteria paniculata Arbutus unedo Pyrus pyraster Fraxinus ornus Amelanchier lamarckii Cytisus scoparius Crataegus monogyna Ceanothus spp Hypericum calycinum Ceratostigma plumbaginoides Each of the containers is designed not to excessively affect the root growth of the plant, preventing root-related issues.

[49] Moreover, the anchoring systems involve not only the basins but also individual plants, which are protected by temporary, base, and redundant fastening devices to prevent overturning or falling, especially under extreme and unexpected environmental conditions.

Notably, the use of lapillus, a porous volcanic scoria, is employed due to its high water retention capacity, excellent cation exchange properties, and long-lasting durability.

[48] Each tree species in the Bosco Verticale is uniquely identified by a sequence of numbers and alphabetical characters based on the plant's scientific name and location (floor and terrace).

[59] Although built on a terrain with ideal lithological conditions and limited influence of the underlying groundwater, the Bosco Verticale is equipped with an energy dissipation system that effectively dampens vibrations.

The adoption of this technology is necessary to prevent the propagation of potential seismic waves and, especially, vibrations induced by the transit of trains on the M2 and M5 metro lines, located to the north and east of the site, respectively.

[60] The presence of the two metro tunnels, with the extrados only 3.5 meters away from the foundations of the two towers,[61] poses a significant source of interference due to anomalies in the guidance of rolling stock and irregularities in the rail structure.

[62] The brick walls are connected to the substructure using T-shaped brackets, while the slabs are mechanically fixed and overlaid with milled ceramics and grooves with aluminum profiles, where the four support hooks are attached.

A strip of structural adhesive between the back of the slab and the side wings of the profile is applied to ensure proper load distribution in windy conditions.

[62] To increase robustness and resistance and provide an adequate support system, the load-bearing walls are constructed using regular brick blocks (25.0×19×48 cm) rectified to a specific weight of 800 kg/m³.

[62] Stainless steel (18% chromium, 8% nickel) clamps, equipped with anti-drip washers and hanging outward, are also applied to maintain thermal insulation properties without compromising the structural integrity.